Intra Pulse Code Modulation (IPCM) blocks are blocks of uncompressed video or image samples where luma and chroma samples are coded in the coded stream. These blocks are used in the case when the entropy coding unit produces more bits rather than reduces bits when coding the blocks of image samples. In other words, the pixel values of the IPCM blocks are not compressed, an thus the raw pixel values of the original image are used. The IPCM block is introduced in the H.264/AVC video compression standard.
A filtering method in H.264 (the filtering method described in Section 8.7 of the H.264 standard) defines that a filter strength for a boundary between two blocks is normally determined based on the average value of a value aPp derived from a quantization parameter QPp of a first macroblock and a quantization parameter QPq of a second macroblock. No decoding is performed for these blocks. However, post-decoding processing (including filtering such as deblocking filtering) is still performed on the block boundaries which tend to be a cause of deterioration in image quality (for example, see Non-patent Literature (NPL) 1).